AC Not Cooling — Diagnostic Checklist
Step-by-step field checklist to identify why your AC isn't cooling
AC Not Cooling Checklist
Complete each step in order. Flag any item with an abnormal finding or that needs follow-up.
1. Diagnostic Tests
Work through each step in order before moving to parts.
Thermostat Check
Confirm unit has power, set to cooling mode, and set point is below room temp
24V Signal & Contactor Test
Verify 24V is reaching the outdoor unit and contactor is pulling in properly
Capacitor Inspection & Test
Visually inspect and test capacitor MFD — weak or failed capacitor prevents compressor and fan from starting
Evaporator Coil Inspection
Check for ice buildup, blockage, or refrigerant leak at the evaporator coil
Airflow & Filter Assessment
Inspect air filter, ductwork, and supply/return vents for restriction or blockage
2. Parts That May Be Needed
Check parts that need replacement based on your diagnosis.
Air Filter Replacement
Standard 16x25x1 or comparable filter
Run Capacitor Replacement
Standard 35/5 or 40/5 μF capacitor
Contactor Replacement
Compressor or fan contactor
Thermostat Replacement
Basic programmable thermostat
Refrigerant Recharge (R-410A)
Per pound of refrigerant added
Condensate Drain Cleaning
Clear clogged drain line
Blower Wheel Cleaning
Clean debris from blower assembly
Evaporator Coil Cleaning
Professional coil cleaning service
3. Technician Labor
Select the labor time required for this repair.
Service Call (Diagnostic Only)
1-hour diagnostic visit, includes pressure/electrical testing
Repair Labor (1 hour)
Technician time for repair work
Repair Labor (2 hours)
Extended repair work
Repair Labor (3+ hours)
Complex repair or compressor replacement labor
Note: Work through diagnostics in order before selecting parts. Most AC cooling issues are resolved with a capacitor replacement or refrigerant recharge.
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